Emim, the button is not too obvious. It's perhaps 6" back from the bottom front of the glove box, about centered, and is black, perhaps 1/4" diameter.
Again I am surprised to learn that Lexus would added this in the second model year, and also that they did not originally include it on such an expensive car. Go figure.
It is a feature I do like. Just last week I got into my car in the garage and saw a low tire warning light. Walking around the car I found a low right front tire, something I would not have noticed otherwise. And no one is going to drop down the spare tire to check the pressure regularly, so monitoring same is quite nice.
Tom